Eye tracking can be described as a process of measuring a person's point of gaze or the motion of their eye(s) relative to the position of their head. An eye tracker is a known device for measuring eye movement and eye positions. Eye trackers are used to measure rotations, or position, of the eye in one of several ways, but generally fall into three categories: (i) measurement of the movement of an object directly attached to the eye, (ii) measurement of electric potentials utilizing electrodes placed around the eyes; and (iii) optical tracking without direct contact to the eye. Optical based eye trackers are recognized as one of the most widely used designs. In this case an optical device, such as a camera, focuses on one or both eyes, and records their movement as the viewer looks at various types of stimulus. A wide variety of disciplines use eye tracking techniques. These disciplines include: (i) cognitive science: (ii) psychology; (iii) medical research; (iv) marketing research; (v) human to computer interaction; (vi) teleconferencing/webinar; and (vii) education.